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MOUNTAIN WEATHER

MOUNTAIN WEATHER. Monica Spicker 2008. Objectives. Explain basic causes of weather. Identify incoming bad weather on the basis of clouds and altimeter readings. Explain what to do if caught in a lightning storm. Appropriately take weather into consideration in mission planning.

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MOUNTAIN WEATHER

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  1. MOUNTAIN WEATHER Monica Spicker 2008 B M O C

  2. Objectives • Explain basic causes of weather. • Identify incoming bad weather on the basis of clouds and altimeter readings. • Explain what to do if caught in a lightning storm. • Appropriately take weather into consideration in mission planning. B M O C

  3. Causes of Weather • Energy flow along gradient • Temperature differences • Pressure differences • Moisture differences • The bigger the difference, the stronger the wind and other weather effects. B M O C

  4. Large Scale Influences • Prevailing Wind: SW. • Jet Stream. • Mountain Ranges. • Ocean and Lakes. • Season. http://www.crystalinks.com/jetstream.html B M O C

  5. Small Scale Influences • Local topography • Orographic Lifting • Elevation • “Rain Shadow” • “Chinook” • Time of day • Up slope winds in morning. • Afternoon thunderstorms build above ridges. • Down slope winds at night. • Quiet times at sunrise and sunset • Season B M O C

  6. Good Weather • Sinking, stable air • Cool • Dry • High pressure • Counterclockwise air flow (anticyclone) http://library.thinkquest.org/03oct/01054/Cyclone/cyclone.html B M O C

  7. Bad Weather • Rising unstable air • Warm • Wet • Low pressure • Clockwise flow in northern hemisphere (Cyclone) B M O C

  8. Fronts: Warm Front • Warm air over cool air • Comes slowly • Brings much precipitation • Warms up after passage B M O C http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html

  9. Fronts: Cold Front • Cold air overtaking and coming up underneath warm air • Comes quickly, often violently • Thunderstorms B M O C http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html

  10. Warm Front Clouds High clouds • 24 to 48 hours • Sun Halo http://k43.pbase.com/v3/17/317917/1/51687992.PA290515_sunhalo.jpg B M O C

  11. Warm Front Clouds • 24 hours • Cirrus & Mare’s Tails • Cirrostratus • Lenticular clouds B M O C http://www.weatherwizkids.com/cloud.htm

  12. Warm Front Clouds Middle clouds • 12 to 24 hours away! • Altostratus http://www.weatherwizkids.com/cloud.htm B M O C

  13. Warm Front Clouds • Low clouds • Warm front is here! • Nimbostratus and nimbocumulus • Rain or snow http://www.weatherwizkids.com/cloud.htm B M O C

  14. Cold Front Clouds Cumulonimbus • Sudden uplift – very unstable • Reaches to stratosphere – anvil shape • Irregular, direction changing winds • Rain, hail, sleet, lightning • Mammutus clouds are associated with severe winds and tornadoes. http://www.weatherwizkids.com/cloud.htm B M O C

  15. Cumulonimbus buildup from orographic lifting Clouds Tell the Tale! Photo by Fred Spicker, 1973 B M O C

  16. Other Clouds Cumulus = “Fair weather clouds” • Actually indicate high humidity and unstable air • Can develop into local storms. http://www.erin.utoronto.ca/~w3gibo/How%20to%20do%20field%20studies/weather_data1.0.htm B M O C

  17. Lightning Safety • Stay alert for signs of thunderstorm development. • Bolt can go up to 10 miles! • Don’t stand near tall objects, hilltop or terrace edges. • Go down hillside • Stay away from vertical rock walls and caves. B M O C

  18. Lightning Safety • Go to lowest point • Remove metal objects. • Stay away from others. • Minimize ground contact. • Make yourself small & compact. B M O C

  19. Other Signs of Approaching Bad Weather • Altimeter reading rises in a given place means low pressure system approaching. • Changing direction and strength of winds. • Low = shift from N, NE to SE; increasing speed. • Cold front = shift from SE to SW • High = shift from SW to N B M O C

  20. Estimating Wind Speed B M O C

  21. Other Considerations • Weather patterns prior to trip • Current forecast • Use altimeter • Monitor clouds and temperature changes. B M O C

  22. Where to Get Forecasts • NOAA National Weather Service (http://www.nws.noaa.gov/) • Meteorological Service of Canada (http://www.weatheroffice.ec.gc.ca/) • State and Province DOT • Weather Underground – worldwide (http://www.wunderground.com/) • Forest Service Fire Weather • Local news or newspaper B M O C

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